Gas exchanges, fruit growth and yield of ‘ANP-0534’, a blush pear selection, under different irrigation levels

The gas exchanges, fruit growth, tree water relations and yield were studied in an experiment involving a new blush pear selection bred in Tatura (Australia), subjected to three irrigation regimes: standard (100%), deficit (50% of standard) and excess (150% of standard). The gas exchanges of leaves were low during the entire season. There were no differences among treatments during most of the season, with deficit showing a decrease only during the warmest part of the season in late January and February. Fruit development followed an expolinear pattern in mass. Absolute growth rates (AGR, g fruit-1 day-1) were low at the end of cell division, which coincided with the application of regulated deficit irrigation (RDI) to control shoot growth and reduce the amount of water applied. AGR values improved after irrigation started, reaching approximately 2 g day-1 from late December to late January. Despite no differences among treatments during most of the season, AGR values for excess water were higher in February, and fruits grew larger in this treatment, although by a margin of approximately 15% by weight, but requiring 50% more water applied. The number of fruit tree-1 was higher in the standard irrigation treatment than in the excess irrigation treatment, thus contributing to the smaller fruit size in the former treatment; however, even when fruit size was adjusted for the number of fruits tree-1 by covariate analysis there was still larger fruit on the excess irrigation treatment. There were no yield differences among treatments. The experiment revealed a less than proportional advantage to excess irrigation.